Prevotella ruminicola xylose isomerase and co-expression with xylulokinase in yeast for xylose fermentation

Abstract

A xylose isomerase (XI) enzyme which exhibits increased activity and affinity for xylose is produced by strain TC2-24 of the rumen bacterium, Prevotella ruminicola. The gene encoding this enzyme may be used to produce improved recombinant yeast capable of utilizing xylose. The recombinant yeast are preferably transformed with heterologous polynucleotide sequences coding both the P. ruminicola XI, and the xylulokinase (XKS) of a Prevotella species. Yeast transformed with the polynucleotide sequences coding both of these XI and XKS exhibit significantly increased xylose utilization and cell growth on a culture medium containing xylose as the sole carbon source, in comparison to yeast transformed with XKS and XI from other sources.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention is drawn to a novel xylose isomerase enzyme and recombinant yeasts which are able to utilize xylose.[0003]2. Description of the Prior Art[0004]Over 95% of U.S. fuel ethanol is produced using corn. Eventually, it is envisioned that annual corn ethanol production can expand to 12-15 billion gallons, consuming 31% or more of the corn harvest. For this reason, commercializing lignocellulose as a feedstock for further ethanol production has been made a national priority. Despite a growing commitment by industry to move towards these more challenging feedstocks, technical barriers still remain unsolved. One critical need is for more robust microbial strains capable of fermenting the more diverse mixture of neutral sugars released by hydrolysis of lignocellulose. Plant cell wall lignocellulose contains, in order of relative abundance, glucose, xylose, arabinose, galactose, and miscellaneous other sugars. While Sa...

AI Technical Summary

Benefits of technology

[0011]In accordance with this discovery, it is an object of this invention to provide a novel xylose isomerase exhibiting increased activity and affinity for xylose.

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Problems solved by technology

Despite a growing commitment by industry to move towards these more challenging feedstocks, technical barriers still remain unsolved.

While some of these are being pursued for commercialization, they have several defects, including the inability to grow anaerobically on xylose, low tolerance to acetic acid and other inhibitory chemicals common to biomass hydrolysates, and generally low productivity and yields compared to glucose-fermenting Saccharomyces cerevisiae.

Naturally xylose-fermenting yeasts convert xylose into xylitol using xylose r

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